1. Field of the Invention
The invention relates to a valve unit.
2. Description of the Related Art
Conventionally, a gas tank mounted in, for example, a fuel cell vehicle is provided with a valve unit used to control the supply and discharge of high-pressure hydrogen gas reserved in the gas tank. The valve unit includes a body in which a gas passage that provides communication between the inside and the outside of the gas tank is formed, and a valve mechanism used to control the flow of the hydrogen gas flowing through the gas passage. As described in Japanese Patent Application Publication No. 2013-29161 (JP 2013-29161 A), the gas passage is coupled to a pipe extending from external equipment such as a hydrogen gas supply source, via a joint fitted to the body.
Specifically, a body 121 of a valve unit described in JP 2013-29161 A has an fitting hole 123 in which a joint 122 is fitted, as illustrated in FIG. 6. A charging passage 124, which serves as a gas passage through which hydrogen gas is charged into a gas tank, is formed in the body 121. The charging passage 124 opens at the bottom face of the fitting hole 123. The pipe 125 is coupled to the joint 122 to connect the pipe 125 to the charging passage 124.
A check valve 132 that inhibits the hydrogen gas from being discharged externally from the fitting hole 123 is disposed in the charging passage 124. The fitting hole 123-side end portion of the charging passage 124 has a diameter-increased portion 133 that opens at the bottom face of the fitting hole 123, and a valve accommodation portion 134 located adjacent to the diameter-increased portion 133. The valve accommodation portion 134 has an inner diameter that is smaller than that of the diameter-increased portion 133 but larger than that of the other portion of the charging passage 124. The check valve 132 includes: a valve seat 136 having a valve port 135 formed at the center of the valve seat 136; a valve element 137 that moves away from or comes into contact with the valve element 137 to open or close the valve port 135 and the charging passage 124; and an urging member 138 that urges the valve element 137 toward the valve seat 136. When the hydrogen gas is not charged into the gas tank, in the check valve 132, the valve element 137 is urged toward the valve seat 136 by the pressure of the hydrogen gas and the urging force of the urging member 138 to be seated in the valve seat 136. Thus, the valve port 135 of the valve seat 136 is closed. As a result, it is possible to inhibit the hydrogen gas from being discharged from the charging passage 124.
The valve seat 136 is fitted in the diameter-increased portion 133, and is pressed, by a plug 142 disposed in a through-hole 141 of the joint 122, against a step face 143 located between the diameter-increased portion 133 and the valve accommodation portion 134. Thus, the position of the valve seat 136 in the charging passage 124 is fixed (restricted). Therefore, if a worker attempts to remove the joint 122 from the fitting hole 123 by mistake after the hydrogen gas is charged into the gas tank, the position of the valve seat 136 may be offset from the proper position. This raises a possibility that the valve element 137 will fail to firmly close the valve port 135 of the valve seat 136 and the function of the check valve 132 will not be sufficiently fulfilled. Thus, improvement of the reliability of the check valve 132 has been demanded.